Lavalier microphone assembly protected against friction noises

ABSTRACT

A microphone assembly includes a longitudinally elongated microphone capsule which is supported within a substantially cylindrical outer casing having an electrical wire connection entering the casing from one end. The microphone is provided with an acoustic inlet at the opposite end of the casing and it is supported in the casing at least at each end by a vibration absorbing support. The support isolates the microphone capsule from noise transmitted to the outer casing. The support at the acoustic inlet end of the microphone capsule comprises a resilient vibration absorbing annular molding which has an inward and radially extending inner end which bears against a collar of a cap which is fitted over the acoustic ends of the microphone. The outer periphery of the annular molding engages against the inner wall of the casing and is held in place by friction or by an adhesive. The cap includes an annular surface which is arranged over the end of the microphone capsule and it includes a collar forming a &#39;&#39;&#39;&#39;Helmholtz resonator&#39;&#39;&#39;&#39; together with an air chamber defined between the protective cap and the diaphragm of the microphone capsule. The molding holding the cap in position forms a funnel which opens outwardly and is engaged by a perforated cap and its associated ring nut at its outer end.

United States Patent Gorike et al.

[451 Mar. 21, 1972 [72] Inventors: Rudolf Qtirilge, Karl Lemoch, both of Wien, Austria AKG Akustische U. Kino-Gerate Gesellschaft mbl'i, Wien, Austria [22] Filed: Jan. 12,1970

[21] Appl.No.: 2,596

[73] Assignee:

[30] Foreign Application Priority Data Jan. 13, 1969 Austria ..A 300/69 [56] References Cited UNITED STATES PATENTS 3,240,883 3/1966 Seeler ..179/l2l D X 2,205,670 6/1940 Pye ..179/180 1,593,457 7/1926 Lakhovsky 179/180 FOREIGN PATENTS OR APPLICATIONS 1,222,116 8/1966 Germany 179/146 1,279,753 10/1968 Germany ..l79/l2lD Primary Examinerl(athleen -1-1. Claffy Assistant ExaminerThomas W. Brown Att0rneyJohn J. McGlew and Alfred E. Page [5 7] ABSTRACT A microphone assembly includes a longitudinally elongated microphone capsule which is supported within a substantially cylindrical outer casing having an electrical wire connection entering the casing from one end. The microphone is provided with an acoustic inlet at the opposite end of the casing and it is supported in the casing at least at each end by a vibration absorbing support. The support isolates the microphone capsule from noise transmitted to the outer casing. The support at the acoustic inlet end of the microphone capsule comprises a resilient vibration absorbing annular molding which has an inward and radially extending inner end which bears against a collar of a cap which is fitted over the acoustic ends of the microphone. The outer periphery of the annular molding engages against the inner wall of the casing and is held in place by friction or by an adhesive. The cap includes an annular surface which is arranged over the end of the microphone capsule and it includes a collar forming a Helmholtz resonator together with an air chamber defined between the protective cap and the diaphragm of the microphone capsule. The molding holding the cap in position forms a funnel which opens outwardly and is engaged by a perforated cap and its associated ring nut at its outer end. I

9 Claims, 1 Drawing Figure LAVALIER MICROPHONE ASSEMBLY PROTECTED AGAINST FRICTION NOISES SUMMARY OF THE INVENTION This invention relates in general to the construction of microphones and in particular to a new and useful microphone assembly including a longitudinally elongated microphone capsule arranged within a tubular outer casing and supported at a spaced relationship from the inner casing walls by a resilient vibration absorbing member.

The present invention is directed particularly to the mounting of microphones within a casing in a manner to achieve a damping of the noise which is transmitted through the casing and it is particularly applicable to microphones of the Lavalier type which are suspended from the neck on a cord, or chain, or otherwise carried on ones person. With microphones of this type it is not unusual for undesirable noise to be picked up a result of the friction produced between the clothing of a person wearing the microphone and the microphone housing. Since this type of noise generally results, in a very noticeable degree, in interference, various measures have been adapted to prevent this transmission from the microphone diaphragm. One of the best known methods involves the mounting of the microphone. The microphone is generally in the form of a rod shaped capsule which is arranged within a tubular outer casing. The microphone is connected to the outer casing by means of a flexible support which supports the capsule on at least two places along its length. Previously employed supports for this purpose have been in the form of rubber rings arranged between the microphone capsule and the casing or alternately porous flexible diaphragms from which the capsule is suspended. In one known arrangement the flexible support at one of the bearing points is secured to both elements, that is, to both the outer casing and the capsule for example, by means of clamps, screws or adhesives and the flexible support of the other point of attachment is only fastened to one of the elements by means for example of clamps, screws, adhesives or coatings of flexible material. In addition, it may be secured by inserting it elastically into a retaining slot to thus mount the flexible member so that it can move on or along the other element relative to its longitudinal extent.

In order to achieve an effective level of noise suppression when employing this known arrangement the flexible member which is mounted so as to be movable relative to one of the two elements must produce neither too much nor too little friction with the elements with which it is in contact. Thus, manufacturing tolerances must be kept within narrow limits so that production costs are markedly increased. The mounting of an inner microphone element, that is, a capsule on a flexible diaphragm also presents difficulties which are essentially connected with producing the corrective degree of noise suppression.

In accordance with the present invention, there is provided a microphone assembly where the capsule is supported in a manner such that there is a marked reduction of the transmission of noise from the outer casing to the microphone. The elongated microphone capsule is supported within the cylindrical casing preferably by at least two axially spaced vibration supporting elements which isolate the capsule from the noise transmitted to the outer casing. The support for the acoustical end of the microphone capsule comprises a resilient vibration absorbing annular molding which bears against an inner central projecting collar which is formed on a cap which is fitted over the acoustic end of the microphone capsule. The outer periphery of the same molding engages the inner wall of the casing and is held in place either by friction or by an adhesive material. The construction includes a support for the capsule at the end remote from the acoustic inlet by a centering diaphragm in combination with an annular centering member having an elastic sound absorbing material.

In accordance with a feature of the invention the cap which fits over the acoustic inlet end ends of the microphone forms a collar which effectively forms a Helmholtz resonator together with an air chamber defined between the protective cap and the diaphragm of the microphone capsule. The flexible molding advantageously includes a funnel portion which engages at its inner annular end against the collar and which opens outwardly and engages the capsule wall at its outer end. This molding forms a sound inlet which is covered by a member having a plurality of openings therethrough. Preferably the molding is made of a flexible material such as synthetic rubber and it contains a filler material to increase its internal friction.

With the microphone assembly of the invention, it is possible to provide a relatively large mass of flexible material of high internal friction for supporting the microphone capsule. The construction is based on the realization that it is not enough to make the resonant frequency lower than the frequency spectrum of the noise transmitted by the casing and then to damp it, but it is also necessary to convert as much as possible of the energy produced by the parasitic vibrations into heat. This will be successful only if a correspondingly large mass of flexible material of high internal friction is present. In practice synthetic rubber whose internal friction is increased by means of fillers has proved highly satisfactory for this purpose.

A further advantage of the microphone assembly of the invention is that a high frequencies the frequency response to the microphone can be smoothed or pre-emphasized by utilizing the collar on the protective cap in front of the diaphragm as a Helmholtz" resonator or a horn. The air chamber formed between the diaphragm and the protective cap is made so narrow that it has no effect in terms of noise on the acoustic response. In other words, it produces a damping effect. In practice the air chamber is made approximately 0.3 to 0.6 mm. in size so that, in conjunction with the cross sectional area of the acoustic inlet in the protective cap and the funnel shaped molding which extends to the outer sound field, the frequency responsive curve of the microphone can be levelled out at high frequencies at a given leptokurtosis.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The only FIGURE of the drawing is a partly elevational and partly axial sectional view of a microphone assembly constructed in accordance with the invention.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing in particular, the invention embodied thereon comprises a microphone assembly generally designated 12 which includes a longitudinally elongated or rodlike microphone capsule 1 having a forward end provided with an acoustic inlet with a diaphragm 14. The capsule is mounted in accordance with the invention within an outer tubular casing or housing 2 with a small clearance between its outer wall and the interior wall of the housing so as to keep the dimensions of the assembly as small as possible.

The electrical output end of the microphone is provided with a studlike projection 4 to which a centering diaphragm is fastened and rests on inwardly stepped ring portion 5 of a sleeve member 18 located within the casing 2. The diaphragm 3 is held in position by a flange ring 20 which engages around the exterior of the ring portion 5. The ring member 18 may be affixed to the exterior casing such as by a adhesive if desired or necessary.

In accordance with a feature of the invention the acoustic inlet with the diaphragm 14 is covered by a protective cap 6 having a central opening which serves as an acoustic inlet. The opening 7 is surrounded by an annular collar portion 8 of protective cap 6. The collar 8 together with an air chamber defined between the cap and the diaphragm 14 form a Helmholtz resonator. The cap 6 is so arranged that the volume of air contained between the annular surface 9 and the microphone diaphragm 14 is as small as possible. in practice the distance between the diaphragm 14 and the annular surface 9 is approximately 0.3 to 0.6 mm., a gap which is entirely adequate for obtaining a satisfactory degree of damping.

The collar 8 of the protective cap 6 is embraced by an annular molding which includes a frustoconical portion with a radially inwardly and downwardly extending end 16 which bears against the exterior of the collar 8 of the cap 6. The opposite end of the molding flares outwardly and terminates in an annular lip l l which is engaged over the end of the casing 2 and held in position thereon by a nut member 20 which is threaded over the end of the casing and engages over a perforated mouth plate or cover 22.

Molding 10 is preferably made of a resilient material such as synthetic rubber and preferably one which contains a filler which increases its internal friction. As distinct from the prior art arrangements in which an O-ring between the inner and outer elements of the microphone capsule and the casing is provided, the mass of molding 10 is in fact many times greater than that of an O-ring of this type. With the molding 10 therefor the mechanical vibrations produced by friction between the clothing of a person wearing the microphone and the microphone casing 2 can be substantially converted into heat and a marked damping effect can be produced. The outer edge of the molding 10 is provided with the annular lip 11 by means of which it engages in an annular groove in the casing assembly. The molding 10 may be fixed in position by adhesive or by making it a force fit if so desired.

In the embodiment illustrated, the cap 6 is fitted into the microphone system as a separate element in the form of a brass sleeve. It may however be formed by appropriately shaping the inner casing 1, thus eliminating the requirement for the separate manufacture of a sleeve.

The output end of the microphone casing 2 is closed by a fitting 24 having the usual electrical wire connections 26. A disk 29 is supported between the fitting 24 and rings 30 and 32 located within the ring member 18.

What is claimed is:

1. In a microphone assembly, of the Lavalier type arranged for suspension on the user's person, comprising an elongated microphone capsule having a forward end provided with a diaphragm and an acoustic inlet, and supported at least at the forward end and at the opposite end in an outer case by vibration-absorbing supports isolating the capsule from noise transmitted to the outer casing, the improvement comprising the support for said forward end of the microphone capsule including a cap portion defining an outwardly extending annular collar adjacent said acoustic inlet, and a resilient vibration-absorbing annular molding embracing said collar, the outer periphery of said annular molding engaging the inner surface of said casing.

2. A microphone assembly, according to claim 1, in which said annular molding is held in place against the inner surface of said casing by friction.

3. A microphone assembly, according to claim 1, in which said annular molding is held in place against the inner surface of said casing by an adhesive.

4. A microphone assembly, according to claim 1, including a stud-like projection, on the output end of said microphone capsule, secured to a centering member positioned within said casing.

5. A microphone assembly, according to claim 4, wherein said centering member comprises an elastic sound absorbing material.

6. A microphone assembly, according to claim 1, wherein said cap portion comprises a separate protective cap fitted over said microphone capsule at the end adjacent said acoustic inlet.

7. A microphone assembly, according to claim 6, wherein said collar on said protective cap forms, together with the air chamber defined between said molding and said diaphragm, a Helmholtz resonator.

8. A microphone assembly, according to claim 1, wherein said molding is flexible and includes a funnel portion which opens outwardly from said collar to a wide opening which serves as a sound inlet.

9. A microphone assembly, according to claim 1, wherein said molding is made of a resilient material such as synthetic rubber having a filler material therein to increase its internal friction. 

1. In a microphone assembly, of the Lavalier type arranged for suspension on the user''s person, comprising an elongated microphone capsule having a forward end provided with a diaphragm and an acoustic inlet, and supported at least at the forward end and at the opposite end in an outer case by vibration-absorbing supports isolating the capsule from noise transmitted to the outer casing, the improvement comprising the support for said forward end of the microphone capsule including a cap portion defining an outwardly extending annular collar adjacent said acoustic inlet, and a resilient vibration-absorbing annular molding embracing said collar, the outer periphery of said annular molding engaging the inner surface of said casing.
 2. A microphone assembly, according to claim 1, in which said annular molding is held in place against the inner surface of said casing by friction.
 3. A microphone assembly, according to claim 1, in which said annular molding is held in place against the inner surface of said casing by an adhesive.
 4. A microphone assembly, according to claim 1, including a stud-like projection, on the output end of said microphone capsule, secured to a centering member positioned within said casing.
 5. A microphone assembly, according to claim 4, wherein said centering member comprises an elastic sound absorbing material.
 6. A microphone assembly, according to claim 1, wherein said cap portion comprises a separate protective cap fitted over said microphone capsule at the end adjacent said acoustic inlet.
 7. A microphone assembly, according to claim 6, wherein said collar on said protective cap forms, together with the air chamber defined between said molding and said diaphragm, a Helmholtz resonator.
 8. A microphone assembly, according to claim 1, wherein said molding is flexible and includes a funnel portion which opens outwardly from said collar to a wide opening which serves as a sound inlet.
 9. A microphone assembly, according to claim 1, wherein said molding is made of a resilient material such as synthetic rubber having a filler material therein to increase its internal friction. 